One known integrated circuit package has a layered lead structure comprising a transmission layer, an insulating layer, and a base layer. The base layer is a relatively thick layer of copper. The insulating layer is a polyimide dielectric layer laminated onto the base layer. The transmission layer consists of multiple copper foil conductive traces that have been patterned onto the insulating layer. Such a laminated structure is commercially available from Mitsui Toatsu Chemicals Inc. under the trademark KOOL-BASE.RTM..
The layered lead structure is press formed to have radiused ends on a perimeter thereof. The lead structure retains its shape due to the strength and memory of the copper base layer. The press form results in an indentation at a center of the lead structure. An IC is attached to the center and wirebonded to the conductive traces of the transmission layer. The indentation is then filled with molding compound to complete the package. This style of package is termed an integrated leadless chip carrier (ILCC), and the package may be attached to a printed wiring board by engaging the radiused portion of the lead structure along a line tangent to the radius with a surface of the printed wiring board. This attachment to a printed wiring board may be made by using conventional surface mount solder manufacturing techniques.
The above-described ILCC package is not, however, appropriate for millimeter wave integrated circuits due to the frequency limitations of the use of molded packaging and surface mount attachment in a printed wiring board assembly. Additionally, the ILCC exhibits inadequate heat removal capability and it does not provide a complimentary coefficient of temperature expansion (CTE) to the millimeter wave circuit packaged therein.